Abaixo está uma instrução que descreve uma tarefa de geração de SQL, combinada com uma entrada que fornece mais contexto sobre os esquemas de tabela disponíveis. Escreva o código SQL que responda adequadamente à solicitação
 ###Instrução: Qual é a classe do qb, Josh Riddell?
 ###Tabelas: CREATE TABLE roster (roster_id AUTO_INCREMENT PRIMARY KEY, Name VARCHAR, Height VARCHAR, Weight VARCHAR, Class VARCHAR, Position VARCHAR, Hometown VARCHAR) CREATE TABLE dublin_and_south_eastern_railway_1854–1924 (dublin_and_south_eastern_railway_1854–1924_id AUTO_INCREMENT PRIMARY KEY, Type VARCHAR, Fleet numbers VARCHAR, Quantity made INT, Date made VARCHAR, GSR Class VARCHAR, GSR Nos. VARCHAR, Withdrawn VARCHAR) CREATE TABLE geography_and_environment (geography_and_environment_id AUTO_INCREMENT PRIMARY KEY, Island VARCHAR, Nickname VARCHAR, Area VARCHAR, Population (as of 2010) INT, Highest point VARCHAR, Elevation VARCHAR, Age ( Ma ) VARCHAR) CREATE TABLE belmont_stakes_feature_key_prep_races_list (belmont_stakes_feature_key_prep_races_list_id AUTO_INCREMENT PRIMARY KEY, Date VARCHAR, Track VARCHAR, Race VARCHAR, Distance VARCHAR, Surface track VARCHAR, Winning horse VARCHAR, Winning jockey VARCHAR) CREATE TABLE main_race (main_race_id AUTO_INCREMENT PRIMARY KEY, Team VARCHAR, Driver VARCHAR, Laps INT, Time VARCHAR, Grid INT)  
SELECT Class FROM roster WHERE Position = qb AND Name = josh riddell